Most Extrasolar Planet detections use periodic Doppler
velocity variations of the parent star to infer the presence
of a planet. Refinements of this technique have reached
precisions of 1 m/sec and better. At these precisions
periodic flows on the stellar surface may well lead to false
detections. The most likely flows of concern are meridional
motions.

Solar surface meridional motions have unambiguously been
observed. They move towards the pole and have an approximate
shape of the second Legendre Polynomial of order m=1
reaching a maximum surface velocity of about 30 m/sec.
Depending on the inclination of the rotation axis to the
line of sight this would cause a red shift in the spectrum
of integrated sunlight of 8 m/sec when viewed perpendicular
to this axis [sin(i)=1] and a blue shift of 15 m/sec when
viewed along this axis [sin(i)=0]. The Sun is a relatively
slow rotator among G and earlier type stars, so that many of
the stellar effects are likely to be larger.

Of interest is, of course, the temporal variation of this
motion. Observations of solar surface meridional flows go
back to 1967. They appear to show variations but my search
for periodic meridional motion changes is so far
inconclusive. This search is complicated by possible
changing instrumental effects and latitudinal change in
convective blue shift ("limb effect"). The latter is also of
interest for false Extrasolar Planet detection techniques.
It can be evaluated by observing the Doppler shifts for
different line strengths and excitation potential. The
former requires a long time sequence of solar observations
of surface meridional flows using the same, unchanging
instrument. The GONG and SOHO/MDI helioseismology
observatories, now in operation for about one solar cycle,
might provide the necessary data.